Doug's Mountain JournalA Chronicle of Natural History on San Bruno Mountain

Doug Allshouse has been writing his seasonal Mountain Journal for many years. It appears in the quarterly newsletters of the Yerba Buena Chapter of the California Native Plant Society (CNPS). We are very pleased to share his seasonal reflections on the natural history of the Mountain. Together with David Nelson, he is writing "The Natural History of San Bruno Mountain", a long-needed and detailed natural history of the Mountain. The book will be published by the California Native Plant Society.

Summer on the mountain is a mixed bag—mostly gray and wet but occasionally quite pleasant with visible sunsets over Point Reyes. By the time our Indian summer kicks in around September the sun has moved south of the Point which means shorter days are quickly upon us and autumn has arrived. The rain season here starts on July 1 and ends the following June 30. For 2014-2015 we received 21.94 inches of rain on 61 days of precipitation (including trace days of fog) and it beat 2013-2014 by 8.09 inches with 21 more days of rain. That qualifies as an average year at 20-24 inches. The trace days of fog that I mentioned have an extreme effect on the health and welfare of many plant, moss and lichen species. The total trace precipitation received for the year was .78 inches. I mentioned in the last journal that this might be an early year for wildflowers and it was, with one caveat. Thanks to a wet February and a decent March and April the season was extended well into May—an unusually gray May I might add. The four-year drought has caused some poison oak to turn fiery-red by the first week of June; easily 3-4 weeks earlier than last year and by early July the coast red elderberry began shedding its leaves. To balance the early departures we welcome an early arrival—the goldenrod began blooming in late May.

Do gophers prefer walking forward or backward? I have an answer! Plopped right in the middle of the Bog Trail there is this really plump gopher, not moving; and here I am standing about ten feet away engaged in a staring contest that lasts at least a minute. I blink first because I’ve got to get home and begin walking towards it and it moves—backward—off the trail. So there you have it, the answer to the question you have yet to ask. Cross that one off your list!

It’s always a crapshoot when I schedule a field trip on the Ridge Trail and sometimes we get challenging weather—as in windy, foggy and cold or still, sunny and hot. There are great conditions between those two extremes but this year we got the first one. It actually did not start too badly and by the time we got to Blue Blossom Hill we stopped and found some California mustard (Caulanthus lasiophyllus) just off the road. What really caught our attention was a pretty robust infestation of tocalote, a plant in the star-thistle tribe. We pulled about 40 out of the ground before I called a halt and promised to come back and do more damage… and it turned out that a lot more was required. I found so many more plants that I filed for a Site Activity Review with the county to pull and monitor tocalote until September 30. I am a bit north of 3000 plants removed so far. The good news is I see fewer new plants each time out.

One morning walk started out with a lot of wet fog in the air and I was under the eucalyptus and cypress trees in Fog Forest. Looking up I could see a few small patches of blue sky—a sure sign of clearing—and within two minutes the fog had completely disappeared! I was shocked how quickly it happened. Then something magical occurred that I had seen only a few times before. There were fine misty droplets of water floating in the air, coupled with large drops falling straight down from the tree tops making splashing sounds as they struck the understory, and all this was backlit by the sun. Moments like that need to be experienced to comprehend, but to think that 120 seconds earlier it was gray and uninspiring is shocking at best. Foggy mornings are also great for exposing spider webs and none are more impressive than those of the Labyrinth Spider (Metepeira). This particular one contained nine orbs and I mention this because it is the earliest I have seen these webs. They usually appear in late August or September.

Late spring and early summer is a good time for eastern migrants when we see a few Rose-breasted Grosbeaks instead of our native Black-headed Grosbeaks. I was excited to lift my trusty Trailblazers to my eyes to check a bird on top of an elderberry bush to find myself looking at a male Indigo Bunting. It’s been almost four years since the last encounter. In this same area a small flock of Purple Finch families hang out. Imagine my glee when I saw one adult hanging onto a wild oat stem and eating the grass seeds. A few days later I noticed a few strange-looking wild radish plants. I walked over to investigate and lo and behold almost every seed pod had been half eaten! Those finches were doing volunteer weed work. I’m thinking of nominating them for the Jake Sigg Award from Cal-IPC. Also unusual with over-wintering birds on the mountain was: the latest observation of a White-throated Sparrow in San Mateo County, May 22, 2015; a singing Varied Thrush last heard on May 26; and a singing Golden-crowned Sparrow in June and July. This sparrow should have been singing in the boreal forests in Canada or Alaska.

Brush rabbit populations have wild swings in numbers. Several years ago there was a massive die-off of young rabbits. This year is definitely a very good year for local lagomorphs with many new bunnies being seen on the Saddle and the bog. Up near the summit they seem happy to feed on seed heads and stalks of Scouler’s catchfly, munching them to the ground—not good news for future recruits.

Firth Canyon is located at the southern end of Brisbane and it yields some of the rarer species of plants. One is pipevine (Aristolochia) which is a remnant vine from an era when California’s climate was somewhat tropical. It is also the larval host plant of the Pipevine Swallowtail butterfly, a large iridescent blue-black beauty. There is a large patch of pipevine in upper Firth sharing space with coyote brush and one Saturday a few of us got to see about 20 larvae, a few remaining flowers, flying adults and one cocoon all in one spot. One interesting fact about pipevine and the swallowtail is that the toxin in the plant, aristolochic acid, is present in all phases of the butterfly’s life cycle. We also discovered some dwarf brodiaea hiding in the grass nearby which was a nice treat.

On the first day of June I got a wonderful surprise. I saw a Western Tiger Swallowtail butterfly hanging upside-down on a fallen English ivy leaf. I picked up the leaf and placed the butterfly on the back of my hand. He was in immaculate condition and showed no interest in nectaring when I tried to place him on some wild radish flowers so I carried him with me. I finally concluded that he was a new adult and his wings were not quite in good working condition yet so I took the opportunity to admire the gorgeous colors and markings of this magnificent creature. I eventually placed him on a coffee berry bush. Something like this doesn’t happen very often but it reinforces a fact of life. Every day brings something new into your life—a new sight or sound, maybe even a sniff of something—that makes you happy that you took time to walk with nature.